Mixing 4000 PSI Concrete
A 4,000 PSI concrete (or pounds per square inch) is the general type of concrete that is the standard for making driveways, walkways and stairs. There is higher-rated PSI concrete, but the 4000 PSI concrete is the most common.
Your first step is to determine how much concrete you are going to need. Get enough for your project so there will be a seamless length of concrete instead of different consistencies.
To calculate the cubic volume, measure the width and length of the area as well how thick you will need the concrete to be.
Purchase the mix. It is generally sold in 40 pound bags, each of which will fill about 1 cubic foot of volume. If you need to cover 200 cubic feet, then you will need approximately 200 bags of concrete.
There are also different PSI strengths. When pouring 4,000 PSI concrete, make sure you buy the right mix.
Determine is extra material will be needed to mix the PSI concrete. Sometimes you can just add water, but other mixtures require an aggregate of some kind. Some manufacturers require that sand or gravel be added. If this is the case with the kind of PSI concrete you bought, gather then necessary amount of extra materials now.
Find the place to mix your concrete. If you are doing a small job that requires just a few bags, then a wheelbarrow and shovel will do just fine.
However, if you are going to be building steps, foundation slab, a walkway or other large project, you will be better off renting a barrel mixer.
Begin adding the ingredients together inside the mixer to form the concrete. According to the bag instructions, add the desired amount of each ingredient. Add the cement mix first, followed by the aggregate, and then the water.
Turn on the barrel mixer and let it turn to mix the ingredients together. Keep an eye on it. When the mixture begins to thicken and become a mud, it is ready to use.
Use your PSI concrete rather quickly. While it doesn't set up very fast, you will need to pour it into your form and trowel is flat before it gets too hard.
The amount of water you have in the concrete will determine how much time you have. The trick is, though, that you don't want to add to much water so that it is runny or there is water standing on your concrete after you trowel it level.